Familial hypertrophic cardiomyopathy (FHC) is a hereditary, autosomal dominant disease of heart muscle. Affected individuals may develop complications including cardiac dysrhythmias, congestive heart failure and*sudden death. Identification of the responsible genetic defect would help to identify affected family members and would contribute to our understanding of cardiac muscle growth and development. During the past year, the candidate has identified a DNA probe linked to FHC in a large family. The identification of this probe proves that a gene responsible for FHC is located on chromosome 14. This important finding makes possible the further work described in this grant. Initially, other families with FHC will be studied to determine if FHC is genetically heterogeneous and to provide more accurate linkage data. Other probes will be identified and used to construct a linkage map of the FHC region. This will eventually make genetic diagnosis of family members possible. Finally, a physical map of the FHC region will be developed using pulsed-field gel electrophoresis, paving the way for the ultimate identification of the FHC gene.